Where can I find the timing markings on a m103 engine (190e 2.6L)? I have replaced the chain but I am not sure if the timing is set correctly. I can see an arrow on the top (bigger) gear, but there is no markings on the lower gear by the oil pan. Please help.

The marks for the crankshaft are on the harmonic damper and are referenced by the bracket that holds the hall sender on the timing cover. If you've got that apart then use a dowell to determine when #1 is near tdc. Assemble it there and then re-check after you reassemble the lower timing cover.

Oh by the way, that arrow is not your timing mark. It is there to id the hole for the camshaft dowell. There is another hole that will allow for different cam timing, that you shouldn't use unless you know what you are doing. The cam timing marks are behind the gear. A dot on the cam will line up in the center of the cam tower when at TDC, compression stroke.

You are talking about setting the top gear here at TDC - I will check it out. How do I go about setting the lower (small) gear in the correct position?